Radio frequency transformer



March 3, 1931. HAYDEN 1,794,897

RADIO FREQUENCY TRANSFORMER Filed June 5, 1927 Harald 1?. Hayden $5 144 Gwen e1 I Patented Mar. 3, 1931 UNITED STATES PATENT OFFICE HAROLD R. HAYDEN, F BROOKLYN, NEW YORK, ASSIGNOR. OF ONE-HALF TO ABRAHAM. E. VAN DOREN RADIO FREQUENCY TRANSFORMER Application filed June a, 1927. Serial No. 196,244.

This invention relates to electrical signal receiving systems employing three-electrode Vacuum tubes as detectors and amplifiers, and

, particularly to certain apparatus adapted for use as parts of such a system.

In the preferred embodiment of my invenvention herein disclosed, the system is a multi-stage signal receiving system employing a detector stage followed by several stages of audio-frequency amplification, and each of the audio-frequency stages is coupled to the preceding stage by a so-called resistance coupling; the last audio-frequency stage serving to operate a loud speaker or other signal-translating device. Each stage of the system includes a three-electrode vacuum tube, the filament of which is heated by direct current from any suitable source such as a battery, and, if desired, means may be provided for maintaining the battery charged from a source of alternating current, such as the usual alternating current lighting mains, and the plate circuits of the several tubes are energized from the same source of alternating current through a rectifier and filter.

The antenna circuitfwhich is preferably ufituned, includes the primary winding of a radio-frequency transformer, the secondary of which is in the grid circuit of the detector tube, and the plate circuit of the detector tube includes a third winding, positioned in inductive relation to the secondary or grid circuit winding; the last winding being adjustable to vary the coupling between the grid and plate circuit. The primary, or an tenna winding, and the secondary, or grid winding, serve as a means for transferring signal energy from the antenna circuit to the grid circuit, and the third or plate circuit winding serves to transfer energy from the plate circuit back to the grid circuit to'increase the amplification of the signals. Connected across the terminals ofthe grid circuit winding is a condenser which is' adjustable to tune the grid circuit to the frequency of any desireddncoming signals. One side of this condenser is connected in the usual manner with the filament supply circuit,'and the other side of the condenser is connected to the grid of the detector tube through an 4 -4 of Figure 2 and adjustable condenser of small capacity, and shunting the condenser is a high resistance which is also adjustable.

The particular construction and arrangement of the detector tube grid and plate circuits and associated antenna circuit, form an important feature of the present invention. These circuits are designed to secure a maximum efficiency of operation, including a high degree of selectivity in tuning for the reception of signal carrier waves of different frequencies, and a maximum amplification of the received signals. The antenna, grid circuit and plate circuit windings are designed as an electrically balanced unitary structure, and these windings are so proportioned and arranged relative to one another as to secure a maximum transfer of energy from the antenna circuit to the grid circuit, with minimum resistance and dielectric losses, and these windings, co-operating with the remainder of the plate and grid circuits, permit a large amount of energy to be transferred from the plate to the grid circuit so as to produce high amplifications without 75 producing disturbing effects common to systems of this character. In the embodiment of my invention herein disclosed the antenna grid and plate circuit windings form a three circuit tuner or variometer which is simple and strong in construction, durable and stable in use and may be easily and economicallymanufactured.

Other advantages and objects of my invention'will appear from the following description taken in connection with the accompanying drawing wherein Figure 1 is circuit diagram of a signal receiving system showing one form of my, in-

vention.

Figure 2 is a top elevation showing the construction, arrangement and mounting of theantenna, detector grid circuit and detector plate circuitwindings.

Figure 3 is a sectional view taken on the line 33 of Figure 2.

- Figure 4 is a sectional viewga taken on line Figure 5 is a perspective view of one of the wire holding strips shown in Figures 2 to 4.

Referring to Figure 1 of the drawing, represents an antenna adapted to receive sig- 5 nal waves. The antenna is grounded at 11 through a winding 12 positioned in inductive relation to a winding 13, included in the grid circuit of the detector tube 16. Connected across the terminals of winding 13 is a condenser 18 which is adjustable to tune the grid circuit of the detector to the frequency of any desired incoming signals. One "side of the condenser 18 is connected to the filament of tube 16, and the other side of condenser 18 is connected to the grid of tube 16 through an adjustable condenser .20 of small capacity, and in parallel with the condenser 20 a high resistance 21, which resistance ,is also adjustable. For the-resistance 21 I prefer in many 20 cases t6 employ a resistance having small distributed capacity.

Connected in'series with the plate of detector tube 16 is a winding 22 positioned in inductive relationto the grid circuit wind- 5 ing 13. Winding 22 is adjustable relative to winding 13 so as to alterthemutual inductance between the two windings.

Figures 2 to 5 show my improved variometer, and the arrangement and mounting of antenna winding 12, detector grid circuit winding 13, and operating detector plate circuit Winding 22.- Figures 2 to 4 are drawn to scale, the spacing and other dimensions of ,the windings being one half that employed by me'when used in connection with an overhead antenna measuring. approximately 100 feet to the winding 12, and with a comparatively short ground connection, the total ohmic resistance of the antenna circuit being- 40 3-tenths ohms.

Reference character 140 includes a supporting tube of bakelite or similar insulating material, upon which is wound the winding 13, which is a single layer coil of 42 turns of 45 Number 17 double cotton covered copper- I wire; To the outer face of the tube 140 are secured by bolts 141, above and below the winding 13, six strips 142, spaced from one another as shown, and between two of the 1 5o strips 142 are secured two strips 148. Strips 142 and 148'are formed along their outer sides with a series of transverse grooves or ndtches 147, in-which are seated the turns of the an .tenna winding 12, which, in the present form 'of my invention, consists of a single layer coil of 11 turns of Number 14 bare copper wire. Each of the strips 142 and 148 is formed on its inner side'with a'recess 146, WhlCh provides a s ace for the turns of the J" winding 13 when t e strip is secured to the tube 140. .The ends of the recess 146 serve to retain the winding 13in place on the tube 140, and prevent the turns of the winding e to the cabinet, I may employan angle bracket 165, secured by bolts to the lower end of one from becoming \se'parated alon the tube.

a cross bar, or member 166, which has a central opening therein, through which the shaft 160 extends; the shaft and bar being secured together by means of a screw 167, and the tube 164 being secured to the ends of the cross bar 166 by screws 168, as shown. On the tube 164 is wound the, detector tube plate circuit winding 22, which consists of two coils in series, each consistin of 14 turns of No. 22.

double cotton covere copper wire, arranged symmetrically on opposite sides of the control shaft 160. The shaft 160 at opposite ends extends through the tube 140, and between adjacent turns of the winding 13, the

conducting wire of the winding at these points being bent slightly above and below the shaft, as indicated at 170, so as to leave a space for passage of the shaft. One end of the shaft 160 also extends between adjacent turns of the winding 12, and the turns of windin 12 are bent slightly above and below the shaft, as shown in Figure 4, so as to leave a space for the passage of the shaft. The notches 147 in the strips 148 are'so spaced as to permit the bending of the wire of the windings 12, as indicate The strips 148, between the notches 146, immediately above and below the shaft, are formed with lateral projections 172, havmg aligned outer faces which lie in a plane at right angles to theshaft 160. Secured to these outer faces, and connecting the projections 17 2, is a flat member 174, which is formed with a central opening, adapted to receive and form a bearin for the shaft 160. On opposite sides of t 's central opening, the member 174 carries outwardly extending projections 175,'which are adapted to co-operate with a pin 176 secured to the shaft 160 to limit the turning movement of the shaft. .When the variometer is mounted in a cabinet, the shaft 160' extends through the front panel, and carries at its outer end an operating knob 178 and a pointer 17 9, which may co-operate with a suitable dial to indicate the position of the shaft and winding 22. V v

For the purpose ofsecuring the varioineter in position in the cabinet, the strips 148 may be formed with lateral projections 150, the outer faces of which bear against the rear face of the front cabinet panel, and these projections are formed with inwardly extending screw-headed openings 180, for the receptionof securing screws, which pass through the panel. If desired, inst'ead. -of employing projections 150 for securingthe variometer N the turning of the shaft 160 so that the coil" 22 will remain in the position in which it is adjusted, I employ sleeves 182 mounted on the shaft 160, which hear at their ends against the tubes 140 and 164. In mounting the tube l64.--on the shaft 160, the shaft is insert-. ed through the tubes, sleeves 182 .and, crossv bar 166, and the cross bar is then secured to the shaft 160 and tube 164 by the screws 167 and 168.

by the coupling arrangement between the I date the shaft 160, the successive turns are The terminalsof winding 12 are indicated by reference characters 191 .and 192, which are located at the top and bottom of one of the strips 142, the securing bolts 14:1 for this" strip serving as binding posts for the term'i nals. The terminals of movable coil 22 are connected by means of flexible conductors 199 to binding screw 200', and the terminals of coil 13 connect to bindingscrews 201 as shown. 1

The following are the dimensions ofone coil constructed by me: diameter cylinder 140, 4 inches; diameter-cylinder 164, 1% inches; distance from outside offsecondarywinding L3 to inside of primary winding 12, 1 inch,

length of primary winding 12, 1 inches.

The windings 12 and 13' are symmetrically arranged with respect to one another, and the turns of their windings lie along cylindrical surfaces which are parallel to one another. The spacing and dimensions of the windings is such that a maximum amount'of energy is transferred from the antenna to the grid circuit, and the requisite amplification is obtained plate and grid winding. On the other hand, the spacing of the windings is such as to avoid the occurrence of disturbances or reactions which interfere with accurate tuning of the grid circuit, or which cause the antenna to receive and radiate energy from the grid cir cuit. Relatively large wire is used for thewindings, which minimize the resistance and ohmic loss in the circuits. It is to be noted that the turns of the antenna winding 12 are spaced apart so that-this winding covers substantially the entire outer surface of the grid winding 13. In this manner each turn of each i one of the windings 12 and 13 are in substantially the same spacial relation to adjacent turns of the other winding. Each turn of each winding istherefore equally effective in securing the desired reaction between the" windings. I find that these features are important in securing the results desired. It

is to be noted that windings 12 and 13 'are' each in effect one continuous coil, and except for the small space provided to accommoequally spaced from one another.

With the winding 22 and its adjusting parts removed, the remainder of the strucbeingcut awayji-ntermediate their ends to ture shown in F igures'2 to 5 may be advantageously used as a radio-frequency trans former. Thus, preceding the detector circuits shown in Figure 1, I employ one or more stages of radio-frequency amplification preceding the detector stage, in which case I may employ as radio-frequency couplings, the

windings 12 and 13', constructed andarranged as shown in Figures 2 to 4.

Iclaim:

1. A radio frequency transformer comprising a cylindrical primary Winding consisting of a single layer coil formed of a number of ing substantially the peripheral area of the other winding and each turn of each winding, throughout its length'having substantially the same spacial relation to adjacent turns of the other winding.

' 2. A radio frequency transformer comprising an insulating tube, a single layer cylindrical Winding formed of closely spaced turns wound on said tube, insulating strips extending the length of said winding and secured at their ends to said tube, said strips form spaces through which said winding passes, and a second cylindrical winding formed of-a few spaced turns of relatively large wire wound on said strips',-each 'winding covering substantially the peripheral area I of the other winding and each turn of each Winding having substantially the same spa cial relation throughout its length to adjacent turns of the other winding.

3. A'radio frequency transformer having a no substantially flat resonance response over .,a wave band of approximately ten thousand," cycles, said transformer comprising a cylin drical primary winding consisting of a single layer coil ofrelativelyfew spaced turnsof large wire and a secondary winding consist-; ing of a single layer cylindrical coil ofrela- Y tively. small closely spaced wire, concentric with and havingits geometric center at ap-; proximately the geometric center of the pri- 12o mary winding, each .coilcovering substantially the peripheral area of the-other coil and each turn of each winding throughout its length having substantially the same spacial relation to adjacent turns of the other winding, the length of the secondary winding being half or more the diameter of the secondarywinding.

4. A radio frequency transformer having a substantiallyfiat resonance response .over

a wave band of approximately ten thousand cycles, said transformer comprising a cylindrical primary winding consisting of a single layer coil of relatively few spaced turns of large wire and a secondary winding consisting of a single layer cylindrical coil of rela tively small closely spaced wire, concentric with and having its geometric center at approximately the geometric center of the primary winding, each coil covering substantially the peripheral area of the other coil and each turn of each winding throughout its length having substantially the same spacial relation to adjacent turns of the other winding, and a third cylindrical winding having its geometric center coincident with the geometric centers of said primary and secondary windings, said third winding being rotatable about said center on an axis transverse to all of said windings. I

HAROLD R. HAYDEN. 

